package com.itheima;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test5 {
    public static void main(String[] args) {
        int[] arr = {-1, 0, 1, 2, -1, -4};
        List<List<Integer>> list = threeSum(arr);
        System.out.println(list);
    }

    public static List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> list = new ArrayList<>();
        Arrays.sort(nums);
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] > 0) {
                return list;
            }
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            //双指针法
            int left = i + 1;
            int right = nums.length - 1;
            while (right > left) {
                if ((nums[i] + nums[left] + nums[right]) > 0) {
                    right--;
                } else if ((nums[i] + nums[left] + nums[right]) < 0) {
                    left++;
                } else {
                    list.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    while (left < right && nums[left] == nums[left + 1]) {
                        left++;
                    }
                    while (left < right && nums[right] == nums[right - 1]) {
                        right--;
                    }
                    left++;
                    right--;
                }
            }
        }

        return list;
    }
}
